When a node first comes up on a network, it needs to obtain information that enables it to communicate with destination nodes. In the case of a fixed, wired network, that information may be pre-programmed into the node, as a result of which it is able to immediately communicate with other nodes once it is activated. In other types of networks, however, the node may need to learn about the configuration of the network before it is able to effectively communicate with other desired nodes. For example, a wireless ad hoc subnetwork may have only one, or at most a few, access points via which the nodes of the subnetwork can communicate with destinations outside of the subnetwork. Not all of the nodes in the subnetwork may have direct links to the access point, and consequently they rely upon neighboring nodes to provide a communications path to and from the access point. To facilitate efficient communications within the network, therefore, the nodes may exchange routing information that provides data relating to the quality, length, latency, etc. of various routes to the access point.
When a node is first installed in an ad hoc network, it may go through a discovery process in which it identifies its nearest neighbors, i.e., other nodes with which it has a direct communications link, and which of those nodes is able to provide a path to an access point. The node may continue to exchange information with its neighbors and update routing information, to ensure its ability to reliably communicate with an access point in an effective manner under dynamically changing network conditions. One example of a procedure via which the node establishes a path to an access point is described in U.S. Patent Application Publication No. 2007/0120705.
Another situation in which a node may need to establish, or confirm, routing information is after it has undergone a reboot operation. The reboot may be the result of a variety of different conditions, such as a software upgrade, loss of power, a regularly scheduled maintenance procedure, etc. After rebooting, the node may undergo the full network discovery process, for example of the type described above, to obtain routing information and resume communications. However, this process might require a significant amount of time. it is preferable to employ information that may already be available to the node as a result of network communications that occur prior to the reboot, to enable the node to quickly recover and resume communications after rebooting.
In one particular application, a wireless ad hoc network may be employed to provide communications between a central control facility of an electric utility, and meters that measure customers' consumption of electricity provided by the utility. When an outage occurs in the distribution infrastructure that delivers electricity to customers where consumption measuring electric meters are co-located, the communication nodes of the ad-hoc wireless network associated and co-located with the meters may also lose power, and be required to reboot when the delivery of power resumes. In some cases, the utility control facility may not be aware of the fact that power has been restored to a customer's premises, until the network node that is co-located with the electric meter at those premises rejoins the network and reports that it has resumed operation. When a large outage occurs and service personnel are in the field to restore a fault, it may be desirable for the utility to learn quickly whether power has been restored, and if so to which nodes and which part of the distribution infrastructure. This knowledge enables the utility to determine whether all faults have been fixed and restoration activities may be terminated, or whether other faults still exist and some customers still remain without power.